1. Field of the Invention
The present invention relates to improvements of matrix-type color plasma display panels using gas discharge, and more particularly to an improved black stripe structure provided for better contrast in an surface-discharge ac plasma display panel so as to obtain panels of higher quality.
2. Description of the Related Art
Surface-discharge ac plasma display panels are commercially used as flat and large full-color display devices in various fields. In the typical structure of these panels, a discharge gas is filled the space between a front substrate and a rear substrate, and pairs of display electrodes are formed along display lines on the front substrate. With this structure, surface-discharge between the pairs of display electrodes generates ultraviolet ray emission and allows phosphors provided on the rear substrate to emit visual light, thus performing color display. The pairs of display electrodes on the front substrate are typically covered with a dielectric layer formed of low melting point glass. On the rear substrate, address electrodes extend under the phosphors in a direction intersecting with the pairs of display electrodes, and barrier ribs for separating the discharge space are provided between the adjacent address electrodes.
As described above, the usual type plasma display panels currently in practical use is the so-called reflection type in which light emitted from the phosphors on the rear substrate is viewed through the front substrate. To accomplish clear full-color display, the xe2x80x9ccontrastxe2x80x9d is measured as one of the quality evaluation factors display panels, and thus, improvement of the contrast is a major requirement. In conventional plasma display panels, because phosphor layers on the rear substrate, which are visible through the front substrate, and reflection of external light at the surface of the front substrate are the major factors causing deterioration of the contrast, so-called black stripes are provided between the adjacent display lines on the front substrate to overcome this problem.
As disclosed, for example, in Japanese Unexamined Patent Application Publication No. 09-129142, the conventional black stripes are provided on the same surface of the front substrate on which the display electrodes are disposed so as to fill in the spacings between the adjacent display lines (referred to as reverse slits) and are covered, together with the display electrodes, with the dielectric layer. As a result, the display electrodes, the black stripes formed of black pigment, and the dielectric layer mainly composed of lead oxide lie contacting each other or close to each other on the front substrate, wherein each display electrode consists of a transparent electrode typically composed of ITO and a metal bus electrode composed of copper or the like. This structure causes an unexpected chemical reaction to occur in the fabrication process or the baking process of each component, thereby resulting in problems such as discoloration of the black stripes, which are supposed to be black, or tarnishing of the dielectric layer which is supposed to be transparent. Accordingly, countermeasures for solving these problems lead, to a large extent, to less freedom in the design of the layout pattern or material selection for each component.
Accordingly, it is an object of the present invention to provide a plasma display panel which can be easily fabricated by improving the structure of black stripes, and which has better contrast as much as possible by eliminating reflection factors of external light. Further, it is another object of the present invention to provide a plasma display panel having wider design versatility and more freedom of material selection by providing means for preventing reflection of external light on a rear substrate without complicating the fabrication process thereof.
The main point of the present invention lies in providing the black stripes, which are conventionally provided on a front substrate, between barrier ribs on the rear substrate. The black stripes are not limited to a sequential arrangement between rows or columns of the matrix, but may include an arrangement in which individual stripes are discretely provided corresponding to dots. Hereinafter, the black stripes are referred to as black material layers.
To this end, the present invention is made as will be described further in detail.
A plasma display panel comprises the following elements: a front substrate; a rear substrate opposing the front substrate across a predetermined discharge space; a dielectric layer; a plurality of display electrodes covered with the dielectric layer and extending in a first direction; a plurality of address electrodes extending in a direction intersecting the first direction; a plurality of discharge cells provided at the intersections between the display electrodes and the address electrodes; a plurality of barrier ribs formed in a predetermined pattern for separating the matrix of the discharge cells in at least one of the row direction and the column direction of the matrix, the pattern defining a plurality of non-discharge cavities in the portions of the barrier ribs corresponding to the non-discharge areas between adjacent rows or columns of the discharge cells; a plurality of phosphor layers provided in the discharge cells defined by the pattern of the barrier ribs; and a plurality of black material layers formed in the non-discharge cavities. The dielectric layer and the display electrodes are formed on the front substrate. The address electrodes, the discharge cells, the barrier ribs, the phosphor layers, the non-discharge cavities, and the black material layers are formed on the rear substrate.
The structure of the plasma display panel according to the present invention eliminates the black stripes on the front substrate, leading to more freedom in material selection without suffering from the known problem of tarnishing of the component members of the display panel. Further, the non-discharge spaces are provided in the barrier ribs formed on the rear substrate and the black material layers functioning as the black stripes are formed in the non-discharge cavities corresponding to the non-discharge spaces. Thus, this structure serves to form the black material layers in a subsequent process which is similar to that of forming the phosphor layers, thereby allowing the plasma display panel to have excellent contrast without complicating the structure and the fabrication process thereof.